Solitary Median Maxillary Central Incisor Syndrome: A Case Report of a Unique Dental Anomaly.

Solitary median maxillary central incisor (SMMCI) syndrome is complex and usually develops 35-38 days postconception during the intrauterine period. A noteworthy discovery is that just one central incisor in the maxillary alveolus, found exactly on the centerline, is present in both deciduous and permanent dentitions with other congenital anomalies. Around one in every 50,000 live babies exhibits this abnormality. This report describes the case of a 13-year-old female patient with SMMCI syndrome with a complaint about an unsightly appearance due to a single large upper front tooth. We underline the importance of increasing clinician awareness of SMMCI syndrome and the need for a multidisciplinary approach to its care.

Influence of Access Cavities on Maxillary Central Incisor Fracture Resistance: Finite Element Study.

INTRODUCTION AND AIMS: Altering the position and orientation of the root canal access cavity passway, or modifying the reduction of dentin volume, can influence the strength of dentition. This study aimed to compare the effects of different access cavities on the biomechanical performances of maxillary central incisors with a finite element analysis. METHODS: Based on the micro-computed tomography (CT) scan of a maxillary central incisor, the finite element models of the intact tooth and teeth with 4 access cavity designs: conservative incisal access cavity, incisal access cavity, conservative access cavity, and traditional access cavity were generated. Simulated occlusal forces were applied at the incisal edge of the incisor in the finite element analysis procedure. RESULTS: The maximum von Mises stress and maximum principal stress in the cervical area are highest in the traditional access cavity group, followed by the conservative access cavity group, incisal access cavity group, and conservative incisal access cavity group. CONCLUSION: The conservative access cavities minimise the extent of dentin removal from the cervical region, protecting the mechanical behaviour of the incisor. Moving the access cavity entry point to the incisal edge also improves the fracture resistance of the incisor. CLINICAL RELEVANCE: This study's findings would help clinicians select the most appropriate endodontics access cavity method when performing the root canal on maxillary central incisors.

Comparative evaluation of two different dental age estimation methods using tooth pulp: A CBCT study.

AIM: To estimate the age of an individual based on 3D radiographic evaluation of pulp width of maxillary central incisor. MATERIALS AND METHODS: This study included 185 CBCT images of individuals within age range of 14-64 years. Images were evaluated for maxillary central incisors and pulp width measurements were taken from cementoenamel junction and middle third of root. Obtained data was subjected to correlation and regression analysis from which the age of an individual was predicted. Results of the present study were compared with another study by the same authors. RESULTS: A negative linear relationship was obtained between age and pulp width. The standard error of estimate (SEE) in sagittal section was 11.36 years and that in coronal section was 11.23 years. The coefficient of determination for sagittal section was 0.107 and for coronal section was 0.127. An obtained regression formula was highly significant. Division of samples into various age groups reduced SEE drastically. CONCLUSION: It can be concluded that pulp width of maxillary central incisor is a reliable indicator of age estimation.

Investigation of the Mesiodistal Angulations of Maxillary Canines and Central Incisors for Missing Bilateral Maxillary Lateral Incisor.

(1) Background: A missing bilateral maxillary lateral incisor (MBMLI) causes aesthetic and functional problems and a multidisciplinary approach is required for treatment. This study aimed to compare the changes in the mesiodistal axial angulations of the maxillary canines and central incisors with orthodontic treatment of MBMLI. (2) Methods: A total of 56 patients with MBMLI were included in the study, and three groups were formed: the control group (Group 1, n = 20) with untreated ideal occlusion and the space opening (Group 2, n = 20) and space closure (Group 3, n = 16) groups as treated study groups. The mesiodistal angulations between the long axes of the maxillary right canine (tooth no 13), right central incisor (tooth no 11), left central incisor (tooth no 21) and maxillary left canine (tooth no 23), and the bicondylar plane, were measured on the panoramic radiographs taken pre (T0) and post treatment (T1). p < 0.05 was accepted for statistical significance. (3) Results: At T0, while there was no significant difference between the mesiodistal angulations of the right-left maxillary canines and central incisors in all groups (p > 0.05), the mesiodistal angulations of the canines in the Group 1 were significantly higher than the study groups (p < 0.05). With treatment, while the mesiodistal angulation of the canines increased in Group 2, it decreased in Group 3 (p < 0.05). On the other hand, the mesiodistal angulation of the central incisors decreased in Group 2 and did not change in Group 3 (p > 0.05). At T1, the mesiodistal angulation of the canines was found to be lower in Group 3 than in Groups 1 and 2, while the angulation of the central incisors was found to be lower in Group 2 compared to Group 1 (p < 0.05). (4) Conclusions: In the orthodontic treatment of MBMLIs, changes in the mesiodistal angulations of the maxillary canine and central incisors should be taken into account for satisfactory outcomes. It was concluded that there should be a tendency to select the space closure method in which normal mesiodistal angulations are obtained in maxillary central incisors for aesthetics and planned incisor position, and also at a low cost.

DISP1 deficiency: monoallelic and biallelic variants cause a spectrum of midline craniofacial malformations.

PURPOSE: DISP1 encodes a transmembrane protein that regulates the secretion of the morphogen, Sonic hedgehog (SHH), a deficiency of which is a major cause of holoprosencephaly (HPE). This disorder covers a spectrum of brain and midline craniofacial malformations. The objective of the present study was to better delineate the clinical phenotypes associated with DISP1 variants. METHODS: This study was based on the identification of at least one pathogenic variant of the DISP1 gene in individuals for whom detailed clinical data were available. RESULTS: A total of 23 DISP1 variants were identified in heterozygous, compound heterozygous or homozygous states in 25 individuals with midline craniofacial defects. Most cases were minor forms of HPE, with craniofacial features such as orofacial cleft, solitary median maxillary central incisor (SMMCI), and congenital nasal pyriform aperture stenosis (CNPAS). These individuals had either monoallelic loss-of-function variants or biallelic missense variants in DISP1. In individuals with severe HPE, the DISP1 variants were commonly found associated with a variant in another HPE-linked gene (i.e. oligogenic inheritance). CONCLUSION: The genetic findings we have acquired demonstrate a significant involvement of DISP1 variants in the phenotypic spectrum of midline defects. This underlines its importance as a crucial element in the efficient secretion of SHH. We also demonstrated that the very rare SMMCI-CNPAS combination is part of the DISP1-related phenotype. The present study highlights the clinical risks to be flagged up during genetic counseling after the discovery of a pathogenic DISP1 variant.

A retrospective analysis of the patient journey for children with an unerupted maxillary central incisor.

BACKGROUND: Maxillary central incisors (MCI) are the third most impacted teeth. Timely multidisciplinary management is indicated as unerupted incisors can cause functional- and appearance-related distress. AIM: To assess the patient journey for children with unerupted MCI, including referral, clinical assessment, surgical management and follow-up treatment, and highlight areas for improvement, as well as identify factors impacting orthodontic treatment burden (OTB). DESIGN: A retrospective service evaluation of children aged 6-16 years who had surgical management of unerupted MCI under general anaesthetic (GA) between 2018 and 2021. RESULTS: Fifty-two children with 62 unerupted MCI were identified. Mean age at referral was 8.8 years. Most children (82.7%) had supernumerary teeth in the anterior maxilla. Mean time between listing for GA and surgery increased from 4.3 to 15.2 months following the COVID-19 lockdown. Mean age at surgery was 10.4 years. Supernumerary removal and incisor exposure and bond was the most common treatment (56.6%). Most patients required hospital orthodontic treatment post-surgery (65.4%). CONCLUSION: Most children referred were below 9 years (60.1%); these children had reduced OTB compared to those who had been referred at an older age. Stage of root development was also a significant predictor in OTB. An unexpected finding was that conical supernumeraries were found to prevent MCI eruption.

CBCT analysis of the relative position between maxillary central incisors and alveolar bone in Southern Chinese adults / 口腔疾病防治

Objective@#Exploring the position and bone wall thickness characteristics of the maxillary central incisors in Southern Chinese adults to provide a clinical reference for the design of immediate maxillary central incisor implantation surgery.@*Methods@#The hospital ethics committee approved the study, and the patients provided informed consent. CBCT images of 990 adult patients (aged 20-79 years) from the Stomatology Hospital (January 2018 to December 2021) were categorized based on the dental arch form and age-sex groups. Sagittal CBCT images of the maxillary central incisors were used to measure the labial and palatal bone thickness wall at 4 mm the CEJ to apical, the middle of the root, and the angle between the tooth long axis and the long axis of the alveolar process, to compare the thickness of the labial and palatal bone walls in samples of male and female patients, and to explore the relationship between the angle between the tooth long axis and the alveolar process long axis in samples of male and female patients in different age groups (20-39 years; 40-59 years; 60-79 years).@*Results@#Significant differences were found in the labiopalatine side of the alveolar bone of the maxillary incisor root position. A total of 95.8% (948/990) of the maxillary incisors were positioned more buccally, 4.1% (41/990) were positioned more midway, and 0.1% (1/990) were positioned more palatally. The thicknesses of the bone wall at the CEJ of 4 mm below the palatal side, the middle of the root, and at the apex were greater (1.82 ± 0.56 mm, 3.20 ± 1.10 mm, and 7.70 ± 2.00 mm, respectively) than those at the labial side (1.21 ± 0.32 mm, 0.89 ± 0.35 mm, and 1.86 ± 0.82 mm, respectively), with statistical significance (P<0.05). Male bone wall thickness was generally greater than female bone wall thickness (P<0.05). The angle between the long axis of male teeth and the alveolar bone was 14.77° ± 5.66°, while that of female teeth was 12.80° ± 5.70°, with a statistically significant difference (P<0.05). The angle between the long axis of teeth and the alveolar bone in the 40-59-year-old group and the 60-79-year-old group was greater than that in the 20-39-year-old group, and the difference was statistically significant (P<0.05).@*Conclusion@#A total of 95.8% of adults in South China have maxillary central incisors with root deviation toward the labial bone cortex. The thickness of the labial bone wall is much thinner than that of the labial bone wall, which is the middle of the thickness of the root. In Southern Chinese adults, the angle between the upper central incisor and the long axis of the alveolar bone in males is greater than that in females, and the degree of the angle increases with age. It is recommended to pay attention to the thickness of the bone wall around the root and the angle between the teeth before immediate implantation surgery to choose a reasonable implantation plan.

Correlation Theory of the Maxillary Central Incisor, Face and Dental Arch Shape in the Serbian Population.

Background and Objectives: According to the modified Williams theory, the shape of the maxillary central incisor corresponds to the shape of the maxillary alveolar ridge (dental arch) and the shape of the face. Moreover, the standards of beauty suggest that the center of the face of an individual with a full set of teeth should match the center of the maxillary and mandibular dental arches. The purpose of this study is to conduct a comparative cross-sectional study on the matching of the shape of the face, maxillary central incisor and maxillary dental arch as well as the matching of the midfacial line and dental arches in subjects with complete dentition. Materials and Methods: The study included 90 subjects of both sexes. The matching of the shape of the face and midfacial line, i.e., dental arches and maxillary incisors, was determined by analysing photographs, whereas the shape of the dental arch was determined by analysing plaster models. Results: No significant gender-related differences were found either in the shape of the maxillary central incisor that matched the shape of the maxillary dental arch (p = 0.349) or in the shape of the dental arch that matched the shape of the face (p = 0.697). However, a significant difference was noted in the shape of the teeth that matched the shape of the face (p = 0.043), which was more significantly impaired in men. In addition, the matching of the mid-face and the mid-dental arch was significantly greater in women (p = 0.016). Conclusions: The modified Williams theory was confirmed in most subjects, thus it can be considered a relevant guideline when determining the shape of teeth after their loss. The highest percentage of matching in both sexes was with the shape of the face and dental arch. There was no positive correlation between the middle of the maxillary and mandibular dental arch in most cases.

Correlation between head circumference and mesio-distal width of the maxillary central incisor: a cross sectional study among three different population groups.

The size and shape of a tooth vary between individuals of different ethnic groups and genders because of the influence of different genetic factors. The information regarding the different anatomical factors using maxillary anterior teeth is very scanty. Thus to give more clarity, a study was planned to assess the correlation between head circumference and tooth-mesiodistal width among children of different ethnic origins.The study was carried out on 210 children aged 7 to 12 years in schools at Abha, Saudi Arabia.The mesiodistal (MD) width of the central incisor was measured using a digital vernier caliper. A Meter tape ruler was used to measure the Head/Cephalic dimensions. The data obtained were subjected to statistical analysis using IBM SPSS 20.0, and the results were analyzed. It was found that mean MD tooth width and head circumference were maximum in Saudi children, followed by South Asian and Arab/African, with an insignificant statistical difference (p-value > 0.05). Correlation between MD dimensions of maxillary central incisor with head circumference was statistically significant (p-value < 0.05) among Saudi and South Asian populations, whereas statistically insignificant (p-value > 0.05) difference between Saudi and Arab/African populations. It was concluded that there exist the ethnic differences between tooth-mesiodistal width and head circumference dimensions of children. A positive correlation between head circumference and mesiodistal width of the central incisor was determined.

Measurement of the Dentin Wall Thickness of the Maxillary Central Incisor in Relation to the Stage of Root Development: A Pilot Study.

Objective: The aim of this study was to determine the average dentin wall thickness (DWT) of the maxillary central incisor (MCI) required for performing finite element analysis (FEA) models of root development. Material and methods: A total of 137 intraoral periapical radiographs of MCI in children aged 7 to 11 years were examined and then classified into 5 groups according to root development stages, which included 1/2 of root development (S1), 3/4 of root development (S2), more than 3/4 of root development (S3), complete development with wide-open apex (S4) and complete development with closed apex (S5). DWT was measured at three reference (horizontal) lines: at a distance of 1 mm from the apex (M), 4 mm from the apex (L) and at the cervical line (K). The distal dentin wall thickness (M1, L1, and K1), the pulp thickness (M2, L2, and K2), the mesial dentin wall thickness (M3, L3, and K3), and the apex thickness (N) were measured using the diagnostic software Soredex Scanora 5.1.2.4. Statistical analysis compared the values of the parameters K, L, and M between developmental stages (multivariate ANOVA) and the linear correlations between the parameters (Pearson's correlation analysis). All analyses were performed at significance level α = 0.05. Results: There were statistically significant differences between the developmental stages for parameters L and M, while no significant differences were found for parameter K. Most of the correlations between the parameters were statistically significant, with the values of the Pearson correlation coefficient R > 0.6 considered practically significant. All parameters on the same reference line for distal and mesial dentin wall thickness and for pulp thickness correlated well with each other (R = 0.46 - 0.68), but there was no statistically significant correlation with total root thickness on the same reference line (parameters K, L, or M), except for parameter K3 (R = 0.42). Conclusion: Despite the limitations of this study, the mean values of the selected parameters for the 5 groups of developmental stages of the maxillary central incisor could be used to model dentin wall thickness using finite element analysis.

The Evaluation of the Relationship Between Intercondylar and Intercanine Distances, Maxillary Central Incisor Width, and Various Facial Forms: A Comparative Study.

Background The intercondylar distance is a predictable and invariable parameter, which is not influenced by the soft tissue limitations and resorption unlike comparable anatomical markers. Limited studies are available on the use of intercondylar distance for the selection of teeth arrangement and its relationship with varying face forms. Aim The study aimed to evaluate the relationship between intercondylar distance and maxillary intercanine tip distances and central incisor width in square, tapering, and ovoid facial forms. Materials and methods The comparative cross-sectional study was performed between January 2021 and August 2022. A convenience sampling strategy was used to include subjects between the ages of 18 and 40 years who had all of their natural teeth. The facial forms of the subjects were detected using a face form indicator and grouped into ovoid (group A), tapering (group B), and square (group C) forms comprising 63 subjects in each group. The intercondylar and intercanine distances and maxillary central incisor width were measured using a digital caliper. The Statistical Package for Social Sciences (SPSS) software (IBM SPSS Statistics, Armonk, NY) was employed to determine the statistical difference between and across the groups using one-way analysis of variance (ANOVA) and post hoc analysis, respectively. The correlation between the variables was determined by the Pearson correlation test. Results The average age of the subjects was 24.55±3.47 years, and the age distribution was found to be statistically insignificant between the groups (p=0.63). The study consisted of 21% of males and 79% of females. The mean intercondylar distance was 125.2 mm in ovoid, 123.1 mm in tapering, and 125.9 mm in square face forms (p<0.01). The mean intercanine distance was 34.82 mm for ovoid, 37.11 mm for tapering, and 37.04 mm for square facial forms (p<0.01). Similarly, the mean central incisor width was 9, 7.84, and 8.51 mm for ovoid, tapering, and square facial forms, respectively (p<0.01). The ratio of intercondylar and intercanine distances in ovoid, tapering, and square faces was 1:3.59, 1:3.31, and 1:3.39, respectively. The ratio of intercondylar and central incisor width was 1:13.9, 1:15.7, and 1:14.7 for the groups A, B, and C, respectively. There was a statistically significant negative correlation between square and ovoid incisor width, square intercanine and ovoid incisor width, tapering incisor width and intercondylar distance, tapering intercanine and intercondylar distances, and tapering incisor width and square intercanine distance. The relationship between intercondylar and intercanine distances and the central incisor width was also revealed to be statistically highly significant (p<0.01). Conclusion When face form is taken into account, tapering face form shows more positive result for the relationship of intercondylar distance with intercanine distance and central incisor width. In patients with edentulous conditions, the intercondylar distance may offer useful measurements for tooth selection.

A rare case of persistent postendodontic symptomatic maxillary central incisor with aberrant canal configuration confirmed by cone-beam computer tomography and its nonsurgical management by retreatment.

Maxillary central incisor is considered the tooth with least anatomical variations. In literature, the prevalence of single root and single canal in maxillary central incisor has been reported as 100%. Only a handful of case reports suggesting more than one root or one canal are available and are mostly associated with developmental anomalies such as gemination and fusion. This article describes a rare case report of retreatment of a maxillary central incisor with two roots with normal clinical crown which was confirmed by cone-beam computer tomography (CBCT). A 50-year-old Indian male patient presented with pain and discomfort on a root canal-treated anterior tooth. Pulp sensibility testing of left maxillary central incisor was negative. Intraoral periapical digital radiograph revealed an obturated canal with suspected outline of a second root which got confirmed with cone shift technique. The tooth was treated under dental operating microscope during which two canals were located and retreatment was completed. Postobturation, CBCT was performed to study the root and canal morphology. Clinically and radiographically, all the follow-up examinations revealed an asymptomatic tooth without any active periapical lesion. The present case report emphasizes the fact that clinicians should approach each case with an open mind having a thorough knowledge of the normal tooth anatomy and should suspect variations in every case to ensure successful endodontic outcome.

Endodontic Management of a Maxillary Central Incisor with two Roots: A Case Report and Literature Review.

Maxillary incisors are typically straightforward cases for root canal therapy. While it is commonly assumed that maxillary central incisors have a single root canal, they may occasionally exhibit variations in their root canal system anatomy. In this report, we present a case of a maxillary central incisor with multiple root canals and provide a review of relevant literature on this anatomical variation. A 13-year-old female with deep carious lesion in tooth 11 was admitted in Department of Endodontics. Following a precise clinical and radiographic examination, a maxillary central incisor with necrotic pulp and chronic apical periodontitis along with unusual root anatomy was found and considered for non-surgical root canal treatment. Successful treatment results depend on various factors and awareness of root canal system anatomy is one of them. Due to an increasing number of reported cases of maxillary central incisors with different anatomy, it is imperative to consider anatomical variations even in the most routine cases.

Stresses in Teeth with External Cervical Resorption Defects Restored with Different Biomimetic Cements: A Finite Element Analysis.

INTRODUCTION: This study compared the stress distributions in teeth with simulated external cervical resorption defects restored with different restorative materials and identified areas of high stress concentration. METHODS: A maxillary central incisor created in a scanned model using HyperWorks software (Altair Engineering Inc, Troy, MI) served as the control. External cervical resorption defects based on Shanon Patel's classification were created (1Bd/2Bd/3Bd) in the scanned model. The defects were restored using mineral trioxide aggregate, Biodentine, glass ionomer cement, and Bioaggregate. On all the models, a force of 100 N was applied on the palatal aspect 2 mm incisal to the cingulum directed at 45° along the long axis of the tooth. RESULTS: The stresses generated in dentin and cementum are less, with a restorative material having a high Young's modulus. For the 1Bd defect, MTA and Bioaggregate showed least stresses in dentin and cementum, respectively, whereas Biodentine had consistently lower stresses in dentin and cementum. Larger defects like 2Bd and 3Bd restored with Bioaggregate exhibited minimum stresses in dentin and cementum. CONCLUSIONS: Bioaggregate and Biodentine replace dentin with maximum stress and maximum strain. Elastic moduli similar to or higher than dentin are preferred for restoring cervical third resorptive lesions of the tooth.

Endodontic Management of Maxillary Central Incisor with Two Roots, and Lateral Incisor with a C-shaped Canal; A Case Report.

The knowledge of anatomical variations in the morphology of root canal systems can affect the successful diagnosis to deliver proper endodontic treatment. The current case report enlightens the endodontic management of an anomalous maxillary left central incisor with two roots/root canals, a C-shaped root canal configuration in a maxillary left lateral incisor identified by three-dimensional cone-beam computed tomography imaging as well as the successful aesthetic rehabilitation of maxillary fractured incisors. The chief complaint of patient was a history of trauma during his outdoor play and consequent broken upper front teeth. Tooth #9 was diagnosed with pulpal necrosis accompanied by asymptomatic apical periodontitis with two relatively dilacerated roots while the maxillary left lateral incisor (tooth #10) was diagnosed with necrotic pulp and asymptomatic apical periodontitis having a C-shaped canal. Endodontic treatment for teeth #9 and #10 were performed, followed by post and core fabrication. Tooth reinforcement was achieved with prefabricated un-polymerized glass fiber post for lateral incisor and Interlig Fiber for central incisor. Intentional root canal treatment of tooth #8 was considered to reduce labial inclination. The anomalous maxillary central incisor with two roots is an unexpected variant during endodontic treatment, and the presence of C-shaped canal in lateral incisors is extremely rare requiring careful diagnosis with radiographs, clinical examination along with additional aids; e.g. Three-dimensional (3-D) cone-beam computed tomography. 3-D imaging has added the advantages of appropriate identification of anomalous anterior teeth and careful location of additional root canal(s) during endodontic treatment.

A coupled-lines system to determine the anteroposterior position of maxillary central incisors for smiling profile esthetics.

OBJECTIVES: To develop a coupled-lines system to determine the anteroposterior position of maxillary central incisors (U1) for smiling profile esthetics. MATERIALS AND METHODS: Thirty Asian females with ordinary and good facial harmony were selected as the study sample and the control sample, respectively. Three-dimensional facial images and 45°- and 90°-angled profiles were collected. The anteroposterior relationships between U1 and upper- and mid-facial soft tissue landmarks were measured. By morphing photos of the study sample, two artificial images were created to represent the well-balanced 45°- and 90°-angled profiles and were further processed with combined variations of soft tissue subnasale (SSn)-Glabella and the mid-point of facial axial points of the bilateral central incisor (mFA)-SSn distances. Esthetic assessments were performed on these images by layperson (n = 94) and orthodontist (n = 94) raters. RESULTS: Both upper- and mid-facial soft tissue landmarks were indispensable in assessing anteroposterior positions of U1 for well-balanced smiling profiles. As assessed in 45°- and 90°-angled profiles, the most esthetically sensitive parameters were mFA-Glabella and mFA-SSn distances. A coupled-lines system was constructed, comprising the Glabella and SSn vertical lines. In smiling profiles with optimal esthetics, the mFA point was at 2 to 5 mm posterior to the Glabella vertical and concomitantly 4 to 7 mm posterior to the SSn vertical, as perceived by orthodontists. Laypersons gave a wider range for mFA-Glabella distances, at 2 to 6 mm. CONCLUSIONS: The coupled-lines system could serve as a reliable reference for determining esthetically optimal anteroposterior positions of U1 for female facial profiles.

The relationship of tooth crown dimensions between first molar and central incisor in maxilla.

The purpose of this study was to investigate a correlation between the cusp dimensions of the first molar and mesiodistal crown diameters of the central incisors in the maxilla. The study materials were composed of dental casts from 29 modern Japanese female subjects with a mean age of 20 years and 8 months. The mesiodistal crown diameters of the maxillary central incisors were measured. The mesiodistal and bucco-lingual crown diameters and the cusp diameters of the maxillary first molars, such as the paracone, metacone, protocone, and hypocone, were also measured. The crown areas and indices of the first molars were calculated. The Spearman's single rank correlation coefficients between the mean values for the crown dimensions of the first molars and the mesiodistal crown diameters of the central incisors were calculated. The hypocone cusp diameter and the hypocone index were the largest compared to those of the paracone, protocone, and metacone cusps. The bucco-lingual diameter and hypocone cusp diameter of the first molars positively correlated with the mesiodistal crown diameters of the central incisors on the same sides. There were positive correlations between the hypocone index of the first molars and the mesiodistal crown diameters of the central incisors. Based on the results, if a large hypocone is observed in eruption of the maxillary first molars, it will be predictable that of the mesiodistal crown diameter of the maxillary central incisor large.

Three-dimensional finite element analysis of the influence of implant site and axial direction on the immediate weight bearing stress of central incisors in different alveolar fossa shapes / 口腔医学

Objective@#To analyze and investigate the effects of implant location and axial direction on the stress distribution of implants, abutments, central screws, and crowns during immediate loading of maxillary mesial incisors with different alveolar fossa morphology based on three-dimensional finite element method.@*Methods@#Referring to the oral CBCT images of a healthy adult, a three-dimensional finite element model was established for immediate implant loading of maxillary central incisors with three alveolar fossa morphs: labial, intermediate, and palatal; different implant sites(apical site, palatal/labial site) and axes(tooth long axis, alveolar bone long axis) were simulated; the established model was loaded with a force of 100 N. ANSYS software was applied to analyze the stress values of the implants, abutments, central screwss, and crownss. @*Results@#The 3D finite element models of 12 maxillary central incisors with different alveolar sockets were successfully established;the implants and their superstructures were least stressed when the maxillary central incisors with partial labial and partial palatal shape were placed along the long axis of the alveolar bone in the palatal/labial position for immediate implant loading;the implants and their superstructures were least stressed when the maxillary central incisors with central shape were placed along the long axis of the tooth in the palatal position for immediate implant loading. The implant and its superstructure were subjected to the least stress when the implant was placed along the long axis of the tooth in the immediate loading position. @*Conclusion@#The bio-mechanical characteristics of the implant and its superstructure are influenced by the different socket morphology, implantation sites and axes. Therefore, in clinical practice, different implantation axes and implantation sites should be developed for different socket morphs.

Effects of Implant Sites and Axial Direction on Stress of Maxillary Central Incisors with Immediate Implantation under Immediate Weight-Bearing: A Three-Dimensional Finite Element Analysis / 医用生物力学

Objective To investigate the influence of implant location and axial direction on stress distributions at the implant bone interface of maxillary central incisors with different alveolar fossa morphology by immediate implantation under immediate weight-bearing. Methods With reference to dental cone beam computed tomography (CBCT) image data from a healthy adult, the three-dimensional ( 3D) finite element models of maxillary central incisors with three types of alveolar fossa ( buccal, mediate, and palatal type) by immediate implatation under immediate weight-bearing were established. Different implant sites ( apical site, palatal / labial site) and axial directions (long axis of the tooth, long axis of the alveolar bone) were simulated. The established models were subjected to 100 N force at different angles (0°, 30°, 45°, 60°, 90°). The stresses in the alveolar bone around the implant were analyzed by the ANSYS software. Results Twelve 3D finite element models of maxillary central incisors with different alveolar fossa morphology by immediate implantation under immediate weight-bearing were successfully established. When alveolar fossa with buccal and mediate shape was applied with immediate implantation under immediate weight-bearing, it was easier to obtain good biomechanical properties of the implant-bone interface when implants were placed at palatal site along long axis of the alveolar bone. When alveolar fossa with palatal shape was applied with immediate implantation under immediate weight bearing, the equivalent stresses on peri-implant alveolar bone were much smaller than those on apical site, regardless of whether the implant was placed along long axis of the tooth or the long axis of the alveolar bone. Conclusions Different alveolar fossa morphology, implant location and axial direction will affect characteristics of implant-bone interface of maxillary central incisors with immediate implantation under immediateweight-bearing. In clinical practice, surgical planning on different axial direction and location of implantation should be developed for alveolar fossa with different morphology.

Síndrome del incisivo central maxilar único: reporte de caso

El síndrome del incisivo central maxilar único es una rara alteración en el desarrollo y formación de órganos ubicados principalmente en la línea media; el cual ocurre de manera temprana entre los días 35 al 38 de vida intrauterina. Su etiología es desconocida, aunque se ha asociado a deleciones de los cromosomas 7 (7q.36.1) y 8, y a mutaciones en el gen Sonic Hedgehog. Presenta una prevalencia de 1/50.000 nacidos vivos y aunque es una anomalía poco frecuente del desarrollo craneofacial, su diagnóstico y tratamiento temprano son importantes para los odontólogos generales o especialistas ya que puede ser un signo de otras anomalías congénitas o del desarrollo graves. Por lo tanto, el objetivo de este caso es reportar la fase inicial de tratamiento en un niño con el síndrome de incisivo central maxilar único quien no había sido diagnosticado anteriormente con este síndrome. Caso Clínico: Paciente masculino de 10 años de edad, procedente de Jamundí, Valle del Cauca- Colombia. Reporta ausencia de órgano dentario superior. En el examen intraoral se observa un incisivo central único sobre la línea media del maxilar, ausencia de frenillo labial y papila incisiva, paladar oval y retrognatismo mandibular. Fue tratado en una primera fase con ortopedia funcional maxilar para mejorar la clase II y está a la espera de iniciar la segunda fase de tratamiento con ortodoncia. Conclusiones: El síndrome de incisivo central maxilar único es un síndrome poco frecuente el cual conlleva múltiples afecciones que interfieren en el normal desarrollo y crecimiento de estructuras anatómicas.

A síndrome do incisivo central superior único é uma alteração rara no desenvolvimento e formação de órgãos localizados principalmente na linha média; que ocorre precocemente entre os dias 35 a 38 de vida intrauterina. Sua etiologia é desconhecida, embora tenha sido associada a deleções dos cromossomos 7 (7q.36.1) e 8, e mutações no gene Sonic Hedgehog. Tem uma prevalência de 1/50.000 nascidos vivos e, embora seja uma anomalia rara do desenvolvimento craniofacial, seu diagnóstico e tratamento precoces são importantes para dentistas gerais ou especialistas, pois pode ser sinal de outras anomalias congênitas ou de desenvolvimento graves. Portanto, o objetivo deste caso é relatar a fase inicial do tratamento em uma criança com síndrome do incisivo central superior único que não havia sido previamente diagnosticada com essa síndrome. Caso clínico: Paciente do sexo masculino, 10 anos, procedente de Jamundí, Valle del Cauca- Colômbia. Relata ausência de órgão dentário superior. O exame intraoral mostra um único incisivo central na linha média maxilar, ausência de frênulo labial e papila incisiva, palato oval e retrognatismo mandibular. Foi tratado numa primeira fase com ortopedia funcional maxilar para melhorar a classe II e aguarda para iniciar a segunda fase do tratamento ortodôntico. Conclusões: A síndrome do incisivo central superior único é uma síndrome rara que envolve múltiplas condições que interferem no desenvolvimento e crescimento normal das estruturas anatômicas.

Solitary maxillary central incisor syndrome is a rare alteration in the development and formation of organs located mainly in the midline; which occurs early between days 35 to 38 of intrauterine life. Its etiology is unknown, although it has been associated with deletions of chromosomes 7 (7q.36.1) and 8, and mutations in the Sonic Hedgehog gene. It has a prevalence of 1/50,000 live births and although it is a rare anomaly of craniofacial development, its early diagnosis and treatment are important for general dentists or specialists since it can be a sign of other serious congenital or developmental anomalies. Therefore, the objective of this case is to report the initial phase of treatment in a child with solitary maxillary central incisor syndrome who had not been previously diagnosed with this syndrome. Clinical case: Male patient, 10 years old, from Jamundí, Valle del Cauca- Colombia. Reports absence of upper dental organ. Intraoral examination shows a solitary central incisor on the maxillary midline, absence of labial frenulum and incisive papilla, oval palate and mandibular retrognathism. He was treated in a first phase with maxillary functional orthopedics to improve class II and is waiting to start the second phase of orthodontic treatment. Conclusions: Solitary maxillary central incisor syndrome is a rare syndrome which involves multiple conditions that interfere with the normal development and growth of anatomical structures.